org.bouncycastle.crypto.macs.Poly1305 Maven / Gradle / Ivy
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package org.bouncycastle.crypto.macs;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.generators.Poly1305KeyGenerator;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.Pack;
/**
* Poly1305 message authentication code, designed by D. J. Bernstein.
*
* Poly1305 computes a 128-bit (16 bytes) authenticator, using a 128 bit nonce and a 256 bit key
* consisting of a 128 bit key applied to an underlying cipher, and a 128 bit key (with 106
* effective key bits) used in the authenticator.
*
* The polynomial calculation in this implementation is adapted from the public domain poly1305-donna-unrolled C implementation
* by Andrew M (@floodyberry).
* @see Poly1305KeyGenerator
*/
public class Poly1305
implements Mac
{
private static final int BLOCK_SIZE = 16;
private final BlockCipher cipher;
private final byte[] singleByte = new byte[1];
// Initialised state
/** Polynomial key */
private int r0, r1, r2, r3, r4;
/** Precomputed 5 * r[1..4] */
private int s1, s2, s3, s4;
/** Encrypted nonce */
private int k0, k1, k2, k3;
// Accumulating state
/** Current block of buffered input */
private final byte[] currentBlock = new byte[BLOCK_SIZE];
/** Current offset in input buffer */
private int currentBlockOffset = 0;
/** Polynomial accumulator */
private int h0, h1, h2, h3, h4;
/**
* Constructs a Poly1305 MAC, where the key passed to init() will be used directly.
*/
public Poly1305()
{
this.cipher = null;
}
/**
* Constructs a Poly1305 MAC, using a 128 bit block cipher.
*/
public Poly1305(final BlockCipher cipher)
{
if (cipher.getBlockSize() != BLOCK_SIZE)
{
throw new IllegalArgumentException("Poly1305 requires a 128 bit block cipher.");
}
this.cipher = cipher;
}
/**
* Initialises the Poly1305 MAC.
*
* @param params if used with a block cipher, then a {@link ParametersWithIV} containing a 128 bit
* nonce and a {@link KeyParameter} with a 256 bit key complying to the
* {@link Poly1305KeyGenerator Poly1305 key format}, otherwise just the
* {@link KeyParameter}.
*/
public void init(CipherParameters params)
throws IllegalArgumentException
{
byte[] nonce = null;
if (cipher != null)
{
if (!(params instanceof ParametersWithIV))
{
throw new IllegalArgumentException("Poly1305 requires an IV when used with a block cipher.");
}
ParametersWithIV ivParams = (ParametersWithIV)params;
nonce = ivParams.getIV();
params = ivParams.getParameters();
}
if (!(params instanceof KeyParameter))
{
throw new IllegalArgumentException("Poly1305 requires a key.");
}
KeyParameter keyParams = (KeyParameter)params;
setKey(keyParams.getKey(), nonce);
reset();
}
private void setKey(final byte[] key, final byte[] nonce)
{
if (key.length != 32)
{
throw new IllegalArgumentException("Poly1305 key must be 256 bits.");
}
if (cipher != null && (nonce == null || nonce.length != BLOCK_SIZE))
{
throw new IllegalArgumentException("Poly1305 requires a 128 bit IV.");
}
// Extract r portion of key (and "clamp" the values)
int t0 = Pack.littleEndianToInt(key, 0);
int t1 = Pack.littleEndianToInt(key, 4);
int t2 = Pack.littleEndianToInt(key, 8);
int t3 = Pack.littleEndianToInt(key, 12);
// NOTE: The masks perform the key "clamping" implicitly
r0 = t0 & 0x03FFFFFF;
r1 = ((t0 >>> 26) | (t1 << 6)) & 0x03FFFF03;
r2 = ((t1 >>> 20) | (t2 << 12)) & 0x03FFC0FF;
r3 = ((t2 >>> 14) | (t3 << 18)) & 0x03F03FFF;
r4 = (t3 >>> 8) & 0x000FFFFF;
// Precompute multipliers
s1 = r1 * 5;
s2 = r2 * 5;
s3 = r3 * 5;
s4 = r4 * 5;
final byte[] kBytes;
final int kOff;
if (cipher == null)
{
kBytes = key;
kOff = BLOCK_SIZE;
}
else
{
// Compute encrypted nonce
kBytes = new byte[BLOCK_SIZE];
kOff = 0;
cipher.init(true, new KeyParameter(key, BLOCK_SIZE, BLOCK_SIZE));
cipher.processBlock(nonce, 0, kBytes, 0);
}
k0 = Pack.littleEndianToInt(kBytes, kOff + 0);
k1 = Pack.littleEndianToInt(kBytes, kOff + 4);
k2 = Pack.littleEndianToInt(kBytes, kOff + 8);
k3 = Pack.littleEndianToInt(kBytes, kOff + 12);
}
public String getAlgorithmName()
{
return cipher == null ? "Poly1305" : "Poly1305-" + cipher.getAlgorithmName();
}
public int getMacSize()
{
return BLOCK_SIZE;
}
public void update(final byte in)
throws IllegalStateException
{
singleByte[0] = in;
update(singleByte, 0, 1);
}
public void update(final byte[] in, final int inOff, final int len)
throws DataLengthException,
IllegalStateException
{
int copied = 0;
while (len > copied)
{
if (currentBlockOffset == BLOCK_SIZE)
{
processBlock();
currentBlockOffset = 0;
}
int toCopy = Math.min((len - copied), BLOCK_SIZE - currentBlockOffset);
System.arraycopy(in, copied + inOff, currentBlock, currentBlockOffset, toCopy);
copied += toCopy;
currentBlockOffset += toCopy;
}
}
private void processBlock()
{
if (currentBlockOffset < BLOCK_SIZE)
{
currentBlock[currentBlockOffset] = 1;
for (int i = currentBlockOffset + 1; i < BLOCK_SIZE; i++)
{
currentBlock[i] = 0;
}
}
final long t0 = 0xffffffffL & Pack.littleEndianToInt(currentBlock, 0);
final long t1 = 0xffffffffL & Pack.littleEndianToInt(currentBlock, 4);
final long t2 = 0xffffffffL & Pack.littleEndianToInt(currentBlock, 8);
final long t3 = 0xffffffffL & Pack.littleEndianToInt(currentBlock, 12);
h0 += t0 & 0x3ffffff;
h1 += (((t1 << 32) | t0) >>> 26) & 0x3ffffff;
h2 += (((t2 << 32) | t1) >>> 20) & 0x3ffffff;
h3 += (((t3 << 32) | t2) >>> 14) & 0x3ffffff;
h4 += (t3 >>> 8);
if (currentBlockOffset == BLOCK_SIZE)
{
h4 += (1 << 24);
}
long tp0 = mul32x32_64(h0,r0) + mul32x32_64(h1,s4) + mul32x32_64(h2,s3) + mul32x32_64(h3,s2) + mul32x32_64(h4,s1);
long tp1 = mul32x32_64(h0,r1) + mul32x32_64(h1,r0) + mul32x32_64(h2,s4) + mul32x32_64(h3,s3) + mul32x32_64(h4,s2);
long tp2 = mul32x32_64(h0,r2) + mul32x32_64(h1,r1) + mul32x32_64(h2,r0) + mul32x32_64(h3,s4) + mul32x32_64(h4,s3);
long tp3 = mul32x32_64(h0,r3) + mul32x32_64(h1,r2) + mul32x32_64(h2,r1) + mul32x32_64(h3,r0) + mul32x32_64(h4,s4);
long tp4 = mul32x32_64(h0,r4) + mul32x32_64(h1,r3) + mul32x32_64(h2,r2) + mul32x32_64(h3,r1) + mul32x32_64(h4,r0);
h0 = (int)tp0 & 0x3ffffff; tp1 += (tp0 >>> 26);
h1 = (int)tp1 & 0x3ffffff; tp2 += (tp1 >>> 26);
h2 = (int)tp2 & 0x3ffffff; tp3 += (tp2 >>> 26);
h3 = (int)tp3 & 0x3ffffff; tp4 += (tp3 >>> 26);
h4 = (int)tp4 & 0x3ffffff;
h0 += (int)(tp4 >>> 26) * 5;
h1 += (h0 >>> 26); h0 &= 0x3ffffff;
}
public int doFinal(final byte[] out, final int outOff)
throws DataLengthException,
IllegalStateException
{
if (outOff + BLOCK_SIZE > out.length)
{
throw new OutputLengthException("Output buffer is too short.");
}
if (currentBlockOffset > 0)
{
// Process padded final block
processBlock();
}
h1 += (h0 >>> 26); h0 &= 0x3ffffff;
h2 += (h1 >>> 26); h1 &= 0x3ffffff;
h3 += (h2 >>> 26); h2 &= 0x3ffffff;
h4 += (h3 >>> 26); h3 &= 0x3ffffff;
h0 += (h4 >>> 26) * 5; h4 &= 0x3ffffff;
h1 += (h0 >>> 26); h0 &= 0x3ffffff;
int g0, g1, g2, g3, g4, b;
g0 = h0 + 5; b = g0 >>> 26; g0 &= 0x3ffffff;
g1 = h1 + b; b = g1 >>> 26; g1 &= 0x3ffffff;
g2 = h2 + b; b = g2 >>> 26; g2 &= 0x3ffffff;
g3 = h3 + b; b = g3 >>> 26; g3 &= 0x3ffffff;
g4 = h4 + b - (1 << 26);
b = (g4 >>> 31) - 1;
int nb = ~b;
h0 = (h0 & nb) | (g0 & b);
h1 = (h1 & nb) | (g1 & b);
h2 = (h2 & nb) | (g2 & b);
h3 = (h3 & nb) | (g3 & b);
h4 = (h4 & nb) | (g4 & b);
long f0, f1, f2, f3;
f0 = (((h0 ) | (h1 << 26)) & 0xffffffffl) + (0xffffffffL & k0);
f1 = (((h1 >>> 6 ) | (h2 << 20)) & 0xffffffffl) + (0xffffffffL & k1);
f2 = (((h2 >>> 12) | (h3 << 14)) & 0xffffffffl) + (0xffffffffL & k2);
f3 = (((h3 >>> 18) | (h4 << 8 )) & 0xffffffffl) + (0xffffffffL & k3);
Pack.intToLittleEndian((int)f0, out, outOff);
f1 += (f0 >>> 32);
Pack.intToLittleEndian((int)f1, out, outOff + 4);
f2 += (f1 >>> 32);
Pack.intToLittleEndian((int)f2, out, outOff + 8);
f3 += (f2 >>> 32);
Pack.intToLittleEndian((int)f3, out, outOff + 12);
reset();
return BLOCK_SIZE;
}
public void reset()
{
currentBlockOffset = 0;
h0 = h1 = h2 = h3 = h4 = 0;
}
private static final long mul32x32_64(int i1, int i2)
{
return (i1 & 0xFFFFFFFFL) * i2;
}
}